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Hi Satish,

> Whenever I take incremental backup it shows a similar size of original 
> volume. Technically It should be smaller. Question is does ceph support 
> incremental backup with cinder? 

IIUC, it would be expected behavior. According to the API Doc[1], 
"size" is "The size of the volume, in gibibytes (GiB)." 
So, it's not the actual size of the snapshot itself. 

What about the "object_count" of "openstack volume backup show" output?
The incremental's one should be zero or less than the full backup at least?

[1] https://docs.openstack.org/api-ref/block-storage/v3/?expanded=show-backup-detail-detail,list-backups-with-detail-detail#id428

-- Masayuki Igawa

On Wed, May 17, 2023, at 03:51, Satish Patel wrote:
> Folks,
>
> I have ceph storage for my openstack and configure cinder-volume and 
> cinder-backup service for my disaster solution. I am trying to use the 
> cinder-backup incremental option to save storage space but somehow It 
> doesn't work the way it should work. 
>
> Whenever I take incremental backup it shows a similar size of original 
> volume. Technically It should be smaller. Question is does ceph support 
> incremental backup with cinder? 
>
> I am running a Yoga release. 
>
> $ openstack volume list
> +--------------------------------------+------------+------------+------+-------------------------------------+
> | ID                                   | Name       | Status     | Size 
> | Attached to                         |
> +--------------------------------------+------------+------------+------+-------------------------------------+
> | 285a49a6-0e03-49e5-abf1-1c1efbfeb5f2 | spatel-vol | backing-up |   10 
> | Attached to spatel-foo on /dev/sdc  |
> +--------------------------------------+------------+------------+------+-------------------------------------+
>
> ### Create full backup 
> $ openstack volume backup create --name spatel-vol-backup spatel-vol --force
> +-------+--------------------------------------+
> | Field | Value                                |
> +-------+--------------------------------------+
> | id    | 4351d9d3-85fa-4cd5-b21d-619b3385aefc |
> | name  | spatel-vol-backup                    |
> +-------+--------------------------------------+
>
> ### Create incremental 
> $ openstack volume backup create --name spatel-vol-backup-1 
> --incremental --force spatel-vol
> +-------+--------------------------------------+
> | Field | Value                                |
> +-------+--------------------------------------+
> | id    | 294b58af-771b-4a9f-bb7b-c37a4f84d678 |
> | name  | spatel-vol-backup-1                  |
> +-------+--------------------------------------+
>
> $ openstack volume backup list
> +--------------------------------------+---------------------+-------------+-----------+------+
> | ID                                   | Name                | 
> Description | Status    | Size |
> +--------------------------------------+---------------------+-------------+-----------+------+
> | 294b58af-771b-4a9f-bb7b-c37a4f84d678 | spatel-vol-backup-1 | None     
>    | available |   10 |
> | 4351d9d3-85fa-4cd5-b21d-619b3385aefc | spatel-vol-backup   | None     
>    | available |   10 |
> +--------------------------------------+---------------------+-------------+-----------+------+
> My incremental backup still shows 10G size which should be lower 
> compared to the first backup.